U.S. Pat. No. 7,755,400, U.S. Pat. No. 4,748,419, and U.S. Pat. No. 4,678,939 disclose a circuit for transmitting a logic signal by using a capacitive isolator as an isolation barrier. The capacitive isolator uses a pair of capacitors to block direct current (DC) between an input side and an output side. For example, in U.S. Pat. No. 7,755,400, the output side is constructed with a high-pass filter (HPF) for edge detection, a window comparator, a reference voltage generator for outputting a DC bias, and a power supply circuit for the comparator, and a RS flip-flop.
The conventional circuit consumes a large amount of power, because a constant bias is necessary for the window comparator, the reference voltage generator, and the power supply circuit.